The present invention relates to magnetic tape cassettes, and more particularly to the structure of upper and lower halves forming a magnetic tape cassette, which structure contributes to a reduction of the number of components and the number of manufacturing steps of the magnetic tape cassette, and to an improvement of the productivity of the same.
Magnetic tape cassettes are employed as recording and reproducing media in audio devices such as magnetic tape recorders and in video devices such as VTRs. An audio magnetic tape cassette is generally composed of a cassette case made up of upper and lower halves, a pair of hubs rotatably mounted in the cassette case, and a magnetic tape wound on the hubs.
When the magnetic tape cassette is in use, generally the magnetic tape is frequently run and stopped in response to the selection of operating modes: a record mode, a playback mode, a fast forward mode, a stop mode, etc. A flangeless type cassette is provided with friction sheets suitable in surface roughness in order to allow the magnetic tape to run as required. More specifically, the friction sheets are used to suitably tension the magnetic tape while it is being run and to prevent the latter from being slackened in the stop mode.
The friction sheets are thin sheets of soft synthetic resin which are placed on the inner walls of the upper and lower halves. The friction sheets may be embossed, or curled, or prevented from being electrically charged, for instance.
The friction sheets are disadvantageous in the following points:
The friction sheets are placed on the inner surfaces of the upper and lower halves in such a manner that the magnetic tape is held between them. Accordingly, it is necessary to provide two friction sheets per magnetic tape cassette, which increases the number of components of the magnetic tape cassette. In addition, placing the friction sheets inside the cassette case suffers from several difficulties. Specifically, before the upper half is joined with the lower half, the upper friction sheet is placed on the upper half, but it is not substantially fixed to the upper half. Sometimes the upper friction sheet is semi-fixedly bonded to the upper half, that is, it is held unstably on the upper half. The above-described operations of placing the friction sheets are carried out manually or by using an assembling machine. In either case, the operation of semi-fixedly bonding friction sheets to upper and lower halves, or the operation of merely placing friction sheets on upper and lower halves must be carried out. The upper and lower halves on which the friction sheets have been placed must be joined together in such a manner that the friction sheets are in alignment with each other. Accordingly, not only is the number of manufacturing steps increased, but also the number of unacceptable magnetic tape cassettes is increased.
The increase in the number of components and in the number of manufacturing steps has resulted in an increase in manufacturing cost.